Toothbrushing has become an established custom for public people in everyday lives in recent years. Toothbrushing aims to prevent dental caries, periodontitis and foul breath and to massage gums, and is widely accomplished by using a toothbrush. Toothbrushes are used to remove plaque adhered to teeth as well as food residue between teeth and to massage gums as well. For conventional toothbrush filaments, mainly monofilament made of uniform resin with round cross-sectional shape has been used. Concerning tip shape of such monofilaments, hemispherical or tapering shape is known. Further, toothbrushes are known which use filaments with only one tip shape or two or more tip shapes for individual tufts which are embedded in tuft holes on the blockhead of the toothbrush.
Further, many kinds of toothbrushes have been further developed, for example, there are toothbrushes designed to remove effectively plaque adhered to tooth surfaces, surfaces between teeth, those between teeth and gums, on molars and so forth or food residue. Toothbrush bristles have been designed in various shapes such as flat cut, angular cut (Japanese Laid-open Utility Model 106522/87), mountain shape cut (Japanese Laid-open Utility Model 82023/91), different level double surface cut, etc. Since filament materials which will not hurt teeth or gums and can effectively remove plaque are preferred for toothbrushes, nylon resins are generally used as filament material of bristles. However toothbrushes are known which use polybutylene terephthalate alone or two materials jointly (Japanese Laid-open Utility Model 81355/77, Japanese Laid-open Utility Model 31837/83) as the bristle material. Toothbrushes are known which use bristles with the same diameter or with two or more diameters (Japanese Laid-open Utility Model 121431/89). Toothbrushes are known in which the filament tips have hemispherical (Japanese Laid-open Utility Model 97923/86) or tapering shapes (Japanese Laid-open Utility Model 31837/83).
As public interest in oral care grows strong in recent years, a number of toothbrushes have been developed, as shown above, to remove effectively plaque which will cause carious teeth or periodontitis. However in the case of toothbrushes whose bristles have all needle like tapering tips to remove plaque adhered to the surface between teeth and gums, because the bristles near tips becomes too thin and too flexible, the bristle tips lose their stiffness necessary to remove plaque sufficiently, and the purpose of toothbrushes to prevent periodontitis cannot be attained after all.
On the other hand, toothbrushes whose bristle ends are round or hemispherical are suitable to clean flat surfaces of teeth or to massage gums. However, it is difficult for such toothbrushes to remove plaque between teeth or in boundary spaces between teeth and gums because the bristle tips are too thick to enter such boundary spaces and reach the plaque therein. That is, it is difficult for conventional toothbrushes having bristles with the same tip shape or those having different tip shapes to clean up in every nook and corner in the mouth.